feat(pygal): implement point-basic (#2587)

## Implementation: `point-basic` - pygal

Implements the **pygal** version of `point-basic`.

**File:** `plots/point-basic/implementations/pygal.py`

---
:robot: *[impl-generate
workflow](https://github.com/MarkusNeusinger/pyplots/actions/runs/20593352389)*

---------

Co-authored-by: github-actions[bot] <github-actions[bot]@users.noreply.github.com>
Co-authored-by: Claude Opus 4.5 <noreply@anthropic.com>
Co-authored-by: github-actions[bot] <41898282+github-actions[bot]@users.noreply.github.com>

Author: github-actions[bot]

plots/point-basic/implementations/pygal.py

@@ -0,0 +1,92 @@
+""" pyplots.ai
+point-basic: Point Estimate Plot
+Library: pygal 3.1.0 | Python 3.13.11
+Quality: 91/100 | Created: 2025-12-30
+"""
+
+import pygal
+from pygal.style import Style
+
+
+# Data: Treatment effects with 95% confidence intervals
+categories = ["Treatment A", "Treatment B", "Treatment C", "Treatment D", "Control"]
+estimates = [2.4, 1.8, 3.2, 0.9, 0.0]
+lower_bounds = [1.6, 0.9, 2.5, -0.2, -0.5]
+upper_bounds = [3.2, 2.7, 3.9, 2.0, 0.5]
+
+# Custom style for 4800x2700 canvas
+ci_color = "#306998"
+point_color = "#FFD43B"
+ref_color = "#888888"
+
+custom_style = Style(
+    background="white",
+    plot_background="white",
+    foreground="#333333",
+    foreground_strong="#333333",
+    foreground_subtle="#999999",
+    colors=(ref_color, ci_color, ci_color, ci_color, ci_color, ci_color, point_color),
+    title_font_size=72,
+    label_font_size=48,
+    major_label_font_size=42,
+    legend_font_size=42,
+    value_font_size=36,
+    stroke_width=6,
+    guide_stroke_color="#e0e0e0",
+)
+
+# Create XY chart for point estimates with confidence intervals
+chart = pygal.XY(
+    width=4800,
+    height=2700,
+    style=custom_style,
+    title="point-basic · pygal · pyplots.ai",
+    x_title="Effect Size",
+    show_legend=True,
+    legend_at_bottom=True,
+    legend_at_bottom_columns=3,
+    show_y_guides=True,
+    show_x_guides=True,
+    dots_size=30,
+    stroke=False,
+    margin_left=120,
+    margin_right=120,
+    margin_top=150,
+    margin_bottom=180,
+    xrange=(-1.5, 4.5),
+    range=(0, 6),
+)
+
+# Map categories to y-values (numeric) - reversed for top-to-bottom display
+y_positions = list(range(len(categories), 0, -1))
+
+# Add reference line at zero first (so it appears behind other elements)
+ref_line = [(0, 0.3), (0, 5.7)]
+chart.add("Reference (x=0)", ref_line, stroke=True, show_dots=False, stroke_width=3)
+
+# Add each CI as a separate series (to avoid connecting lines)
+for i, (low, high, y) in enumerate(zip(lower_bounds, upper_bounds, y_positions, strict=True)):
+    ci_data = [(low, y), (high, y)]
+    # First CI gets label, others are hidden from legend using None
+    if i == 0:
+        chart.add("95% CI", ci_data, stroke=True, show_dots=False, stroke_width=8)
+    else:
+        chart.add(None, ci_data, stroke=True, show_dots=False, stroke_width=8)
+
+# Add point estimates (on top of CI lines)
+point_data = [(est, y) for est, y in zip(estimates, y_positions, strict=True)]
+chart.add("Point Estimate", point_data, dots_size=32, stroke=False)
+
+# Custom y-axis labels with category names - use major labels
+chart.y_labels_major = [5, 4, 3, 2, 1]
+chart.y_labels = [
+    {"value": 5, "label": "Treatment A"},
+    {"value": 4, "label": "Treatment B"},
+    {"value": 3, "label": "Treatment C"},
+    {"value": 2, "label": "Treatment D"},
+    {"value": 1, "label": "Control"},
+]
+
+# Save as PNG and HTML
+chart.render_to_png("plot.png")
+chart.render_to_file("plot.html")

plots/point-basic/metadata/pygal.yaml

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+library: pygal
+specification_id: point-basic
+created: '2025-12-30T09:34:14Z'
+updated: '2025-12-30T09:44:39Z'
+generated_by: claude-opus-4-5-20251101
+workflow_run: 20593352389
+issue: 0
+python_version: 3.13.11
+library_version: 3.1.0
+preview_url: https://storage.googleapis.com/pyplots-images/plots/point-basic/pygal/plot.png
+preview_thumb: https://storage.googleapis.com/pyplots-images/plots/point-basic/pygal/plot_thumb.png
+preview_html: https://storage.googleapis.com/pyplots-images/plots/point-basic/pygal/plot.html
+quality_score: 91
+review:
+  strengths:
+  - Excellent horizontal orientation matching spec recommendation for readable category
+    labels
+  - Clear visual hierarchy with distinct colors for reference line, CIs, and point
+    estimates
+  - Includes reference line at zero as suggested in spec notes
+  - Well-structured code following KISS principles with good use of pygal Style system
+  - Realistic clinical trial scenario demonstrating varied effect sizes and CI widths
+  weaknesses:
+  - Confidence interval lines lack caps/endpoints as suggested in the specification
+    notes
+  - X-axis label Effect Size could include units or be more descriptive